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Pickups Chevrolet Silverado & GMC Sierra 2007/2008 Silverado and Sierra Active Fuel Management Problems
106 messages, Last post on Sep 01, 2009 at 9:04 PM
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I have a new 2008 Sierra with 5.3l engine and about 2,000 miles. Once every week or two, when starting the engine, it sounds like none of the lifters have oil in them. The engine sounds like an old model V8 with mechanical valve lifters that are way out of adjustment. The valve clatter will continue but goes away by shutting off the engine and Immediately starting it again. The oil pressure is good and the dip stick shows oil is full. The noise only happens when the engine is cold or warm. Is AFM in control of the lifters and valves at startup? Has anyone had this problem? Thanks,
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Replying to: astroman2 (Jul 31, 2008 3:08 pm) Let us know if you find out anything.
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Replying to: astroman2 (Jul 31, 2008 3:08 pm) |
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I have the 1500 5.3 with AFM and have noticed an inconsistent vibration at about 55mph. There's a flat smooth stretch of highway I often take going home for about 7 miles and the vibration often occurs there between 50 and 55mph. It feels like I'm going over a course road surface but I'm not. AFM is sometime on and sometimes not. This vibration always occurs when I maintain this 55mph +/- speed for a time. It never happens in town and I have never noticed it at 65+. I've never ntoiced it at idle. Other than that I like the truck a lot. I'm a boring old fart of a driver but I get very good mileage. The lowest fillup I did gave 16.6 and highest has been 22.4. That 22.4 was almost all highway driving. Considering the power and size of this truck I think that's superb.
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Replying to: raymaz (Sep 23, 2008 6:13 pm) |
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| I remember I had a 2003 Silverado with the 4.8 engine. I dualled out the pipes and installed a flowmaster. At 50-55 MPH there was an incredible roar and vibration. Had to keep it above 60 to avoid it. Don't remember having the problem before the exhaust work. | |
| Hi everyone!! my sister just bought a 2008 gm sierra 5.3 ,she has had it for almost 6 months !! and we are experiencing problems she said it was like the gas peddle just went to the floor on her!! she narrowly missed hitting a school bus and chose the ditch instead which ended up being the safest course of action but she did hurt herself !! we had the truck towed back to the dealership and they are now saying that they cannot find a problem for it !!!! If anyone out there has had any similar experiences please let me know as There is a problem and we need to get something done about this | |
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Replying to: misswench (Sep 26, 2008 10:29 am) |
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Replying to: natesms (Jul 31, 2008 6:18 pm) |
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Replying to: gmax6 (Apr 23, 2008 5:39 pm) RPM/Engine Surge: When easing to a stop or after stopping and slowly rolling (by easing off brake, no throttle apply) into my garage, the engine speed will increase surging the vehicle forward. It does not matter if the engine is cold or warm, nor driving for one minute or one hour. The engine speed will increase up to ~1000 rpm or more. The engine speed will surge and slowly come down to ~600 rpm in less than 15 seconds. This problem does not occur all the time, but I can bet on it happening each time I drive The dealer was told by Chevy Tech Service that it is normal. I can't see it normal to have the vehicle speed increase with my foot on the brake. Tafid |
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